Editing Hubbert peak theory (section)

===Air/oxygen===
Half the world's [[oxygen]] is produced by [[phytoplankton]]. The plankton was once thought to have dropped by 40% since the 1950s.<ref>{{cite web|url=http://www.nbcnews.com/id/38451744/ns/us_news-environment#.UgzfIdKOSrN |archive-url=https://web.archive.org/web/20130925132822/http://www.nbcnews.com/id/38451744/ns/us_news-environment#.UgzfIdKOSrN |url-status=dead |archive-date=September 25, 2013 |title=Plankton, base of ocean food web, in big decline  |publisher=NBC News |date=2010-07-28 |access-date=2013-11-03}}</ref> However, the authors reanalyzed their data with better calibrations and found plankton abundance dropped globally by only a few percent over this time interval ([http://wormlab.biology.dal.ca/publication/view/boyce-etal-2014-estimating-global-chlorophyll-changes-over-the-past-century/ Boyce et al. 2014])